Spaceship Design

The engineer in me spends a lot of time thinking about stuff.

Something I've thought about a lot is what crummy designs most spaceships in science fiction are.

Take Enterprise (NCC-1701 and NCC-1701-A): the impulse engine is mounted at the base of the saucer section.  If the secondary hull has much mass (and according to deck plans this is where most of the machinery is) then applying thrust at the top of the boom connecting the primary and secondary hulls will result in spin.  Also frightening in the Star Trek universe is the hundreds to thousands of g of acceleration displayed.  Inertial compensation must be an insanely reliable technology to attempt human-to-goo accelerations.  I assume that the compensators are tied directly to the engines since the crew is still bounced around by other factors.

Then there's Star Wars.  The Millennium Falcon does much better as far as thrust lines go, but everything in Star Wars seems to be an airplane that happens to go to space than space craft.  Windows seem to be primary sensors.  Not to mention that they are FLYING and changing vector like there's wings involved.

The Star Fury from Babylon 5 is a dang good design.  The pilot position is basically laying on their back during thrust, the "wings" are there to get leverage for the steering thrusters, not for lift.  More than once we see them maneuvering independently from their vector.

Then there's SF role playing.

One of my favorite designs to poke at is Traveller's Type-S (Sulliemain) scout/courier.  It's a wedge.  Pretty sharp edged wedge.  It drives me insane.  Traveller requires a large portion of the ship be dedicated to fuel for the jump drive (20% of volume for a jump-2 like the Type-S).  This fuel is liquid hydrogen.  There are two ways to keep hydrogen liquid.  High pressure and low temperature.  Go look at a pressure vessel some time, notice the lack of corners?  Pressure loves to break corners.  The Type S is ALL corners!  Oh, the fuel tankage surrounds the life-section too.  A cryo-plant is never mentioned in any canon material, so it must be pressure doing it all.

You can certainly build a cube to take the same pressure as a sphere of the same volume.  It will be heavier.  Heavier means more material and that means costs more.  You need a reason to use a different shape.  Streamlining to fly in the atmosphere is a good reason.  Except Traveller has some pretty damn miraculous maneuver drives.  The type S can pull 2g for A MONTH.  It also doesn't have to change facing to change vector.  What that means is anything with more thrust than local gravity in Traveller can soft land regardless of its aerodynamic shape.  What making your craft streamlined gives you is you can travel faster in the goo, and that's worth compromising the shape for it; but if you can thrust in any direction at will, you don't need wings.

But a pointy wedge is not your best choice!  A rounded ended cylinder is.  A secant section nose with a hemispherical tail comes out best.  Like a bullet, in fact.  This shape is also efficient in surface area:volume as well (a sphere is the best surface area to volume ratio).  Wedges and squares are less efficient.  A more efficient ratio means less material for the hull skin and less material is cheaper.  No matter what it's made of, that's true.  Less material is always lighter than more; but in Traveller I believe the drives are moving a volume not a mass.  At least performance doesn't seem to be affected by how much cargo you pack into your ship.  28 cubic meters of uranium is the same as water near as I can tell.

Windows are something that comes up time and time again in spaceships in fiction.  Quick!  Go outside and point at Pluto!  Come on, it's RIGHT THERE!  Oh wait, it's a long ways away and not naked eye visible, is it?  Pluto may be small on a solar system scale, but it's going to hurt a lot of you run into it.  And with some of the velocities demonstrated in science fiction, you aren't going to get out of its way in time if you're relying on windows and the Mark I eyeball.  Even a high-magnification telescope is likely not going to give you enough warning, but it's much better.  But once we divorce ourselves from the window we can also move the control room away from a flight-deck or bridge location.  Another truth of materials is transparent is weaker than opaque.  But the future might fix that.  Burying the control room inside the ship is a good plan.  Putting it at the center of mass is also good since when you maneuver you will not be as subjected to centrifugal forces.

Once of the most rational ship designs I've ever seen is in the comic Erma Felna.  They are rounded end cylinders.  Fuel is stored in the ends, drives below the life section in the middle.  There the fuel is cryogenic liquid hydrogen and the maneuver drive is a fusion thruster.  2g is a sprint capability of military ships; not a norm.  Star ships do not land in this universe.  They carry smaller craft which are aerodynamically shaped.

The placement of the fuel is not accidental.  It's ARMOR.  Ablative armor, but armor nonetheless.  What happens if you spack into a sofball sized hunk of rock at the speeds you can attain while thrusting at half a gee for a week?  BANG is what.  With blow-off doors on your tank you can let the fuel take the hit and spread the load out quite a bit.  You want the tankage on both ends because when you're decelerating you're traveling tail-first.

There's lots more on this, but it's all I have for now.

PS: My infamous "dildo" design.

This is your normal everyday Type-S design using Book 5 for the stats (comes out the same as a Book 2 design).  I was very surprised at how much more compact it was as compared to the Supplement 7 design while having the correct volume whereas the Supp 7 plans are about 78 tons as shown.